Existing optical couplers generally exhibit a variation in performance from device to device. For example, the current transfer ratio and speed of an optical device can vary significantly. This can pose a significant problem when one is coupling multiple channels and minimal device-to-device variation is needed to preserve relative channel signal levels.
Part of the problem can be minimized by using multiple channel couplers. However, since the individual optical devices within such couplers may be fabricated from different wafers or different portions of the same wafer, they are not necessarily matched devices. Further, such couplers may not use isolated optical paths for the devices to minimize cross-talk. Thus, even within one package, performance variations persist.
It would be helpful therefore to provide a coupler that can handle multiple signals with minimal channel-to-channel variation in signal transfer performance. Also, it is desirable to provide a coupler that has the maximum number of isolated channels using the least number of pins, to reduce assembly costs and to reduce the required printed circuit board space.